Field of the Invention
The present invention relates to wireless communications systems and, more specifically, to a system that manages the power level of transmitted signals in an ad-hoc communications system.
Background of the Invention
An ad-hoc network is a local area network or other small network, especially one with wireless connections, in which some of the communication devices form a somewhat informal impromptu network, which is sometimes established for temporary communication independent of a dedicated infrastructure, which can require a degree of proximity depending upon the particular network. The wireless device communication system known as Bluetooth® was designed to allow wireless devices to interact with each other in a more informal manner by providing a framework in which to establish ad-hoc networks. In one configuration, a wireless device communicates with a wireless ad-hoc network node. The Bluetooth® specification is an open specification that is governed by the Bluetooth® Special Interest Group (SIG), Inc. The Bluetooth® SIG classifies Bluetooth® devices according to three different power classes, as follows:
Power ClassMaximum Output Power1100 mW (20 dBm)2 2.5 mW (4 dBm)3 1 mW (0 dBm)
Many portable Bluetooth® devices are in Power Class 1 or 2 due to cost and battery life issues. Typically, a Class 1 device requires use of a power control to limit the transmitted power. This will provide up to 100 m of range—sufficient for home networking and other similar applications.
The majority of Bluetooth® devices currently in the market have approximately a 10 meter range. This is sufficient for many point to point communication applications, such as those involving communications with headsets, handsfree car kits, PIM transfers, etc., but as one starts to enter different personal area networks within the home, business, and mobile world, a 10 meter range may be insufficient for seamlessly transitioning between these different environments. Some point to point scenarios (such as communicating with a printer server) require a greater range. For some point to point scenarios, a longer range can improve the user experience by allowing greater freedom of mobility while supporting and maintaining continued communication, even though as the distance between communication participants decrease the shorter Class 2 range would be sufficient for operation and even preferred when battery power is low.
Existing wireless devices are often not configured to dynamically adjust power level of the transmit signal, when the range between the wireless device and the node with which it is communicating changes, including instances in which the appropriateness and/or suitability of a lower power level could be detected. In absence of the capability to dynamically adjust power levels, different applications will often set the level to the maximum level supported by the application. By allowing the dynamic adjustment of the power level, the power usage requirements for supporting the communication can be reduced. This can result in reduced time between battery charges. Also, transmitting an unnecessarily high power level of the transmit signal from a wireless device increases the likelihood that an eavesdropper will be able to intercept the communication.
Consequently, a method that switches between different power levels of the transmit signal according to the range (or other parameter) in support of a communication between the wireless device and another wireless ad-hoc network node would be beneficial.